concretion

noun

1. 1

   the union of diverse things into one body or form or group; the growing together of parts

2. 2

   an increase in the density of something

3. 3

   a hard lump produced by the concretion of mineral salts; found in hollow organs or ducts of the body

   renal calculi can be very painful

4. 4

   the formation of stonelike objects within a body organ (e.g., the kidneys)